1. Technical Field
The present invention relates to a signal processing apparatus for producing an effect according to the content of the input audio signal.
2. Background Art
Recently, a multi-channel audio equipment is spreading. The multi-channel audio equipment denotes an equipment that can reproduce audio sounds with three-dimensional soundscape, by reproducing audio signals in the channels whose number is larger than the stereo 2-channels such as 5.1 channels, or the like (multi-channel), and then outputting these signals from a plurality of speakers that are set up at respective locations of the room (JP-A-8-275300).
In the background art, the content whose multi-channel audio signals can be reproduced in the ordinary home are limited to the movie content recorded in the DVD, or so. In the movie content, the channel assignment indicating which acoustic types of the audio signals should be assigned to respective channels is substantially standardized. The acoustic type is based on content of acoustics. As the content of acoustics, there can be considered talking voices such as one's lines, musical sound such as BGM, or other sounds such as ambient sounds or sound effects. For example, it is general that the talking voices are assigned to the center channel, the musical sounds are assigned to the front left/right channels, and other sounds are assigned to the surround left/right channels.
The multi-channel audio equipment is equipped with the function for performing the sound field control to produce the reverberations of a virtual space such as a hall, or the like, by adding reflected sounds and reverberation sounds to the reproduced audio signals.
However, when the effect such as the reflected sound, the reverberation sound, or the like is added strongly to the talking voices such as one's lines, etc., the articulation is decreased. This makes it hard for the listener to comprehend what the performers are speaking. For this reason, it is common that a controlled amount of sound field on the channel where the talking voices are reproduced is set smaller than those on other channels. As described above, in the case of the movie content, commonly the talking voices such as one's lines, and the like are assigned to the center channel. As a result, in the multi-channel audio equipment in the background art, it is set in advance that a controlled amount of sound field on the center channel should be small and a controlled amount of sound field on other channels should be large or middle.
However, the multi-channel audio content that can be reproduced by the equipment for use at home are diversified on account of the start of the digital terrestrial broadcasting, and the like, and thus the content in which the channel assignment used in the conventional movie, or the like is not employed are increased. That is, the content in which the talking voices are assigned to not the center channel but the front channel or the surround channel are increased.
When such multi-channel audio content is reproduced in the conventional setting for the controlled amount of sound field, the strong reflection or reverberation effect is caused in the talking voices such as one's lines, and the like, and thus a deterioration of the articulation is caused. Also, when the musical sounds such as BGM, etc. are reproduced on the center channel, the sound field effect is not exercised on BGM, so that such problems arise that it is impossible for BGM to enliven the atmosphere, and the like.